Question: Which of the following numbers is a factor of 121? ${4,6,7,9,11}$
By definition, a factor of a number will divide evenly into that number. We can start by dividing $121$ by each of our answer choices. $121 \div 4 = 30\text{ R }1$ $121 \div 6 = 20\text{ R }1$ $121 \div 7 = 17\text{ R }2$ $121 \div 9 = 13\text{ R }4$ $121 \div 11 = 11$ The only answer choice that divides into $121$ with no remainder is $11$ $ 11$ $11$ $121$ We can check our answer by looking at the prime factorization of both numbers. Notice that the prime factors of $11$ are contained within the prime factors of $121$ $121 = 11\times11 11 = 11$ Therefore the only factor of $121$ out of our choices is $11$. We can say that $121$ is divisible by $11$.